This invention relates to an elevator constituted by a plurality of telescopic sections along which a load container can travel, and in particular to an elevator having a respective locking device between each two adjacent telescopic sections.
A known elevator of this type is constituted by a plurality of relatively-movable telescopic sections, all of which can be extended at the same time by actuation of a cable winch. In other words, relative movement takes place simultaneously between all telescopic sections--perhaps with the exception of the first (lowest) telescopic section.
With such an elevator, it is desirable that, when a desired length of extension is reached, all the telescopic sections can be locked together. In the known elevator, this locking takes place by actuating a draw cable associated with the lowermost telescopic section. Actuation of this draw cable effects both the locking between the lowermost telescopic section and the adjacent telescopic section, and the pivoting movement of a pivot body arranged on the lowermost telescopic section. The pivotal movement of this pivot body results in the shortening of a further draw cable which runs from the lower end of the said adjacent telescopic section to the upper end thereof. The shortening of this further draw cable effects both the locking between said adjacent telescopic section and the subsequent telescopic section, and the pivoting movement of a further pivot body. This, in turn, shortens a further draw cable, and so on until all pairs of adjacent telescopic sections are locked together (see DE-PS No. 3,001,410).
This known elevator has the advantage that actuation of a single draw cable results in the actuation of all the further draw cables, thereby resulting in all the telescopic sections being locked together, without the need for a long cable conducted over all the telescopic sections which would have the disadvantage of cable elasticity, and thus inexact response characteristics of the locking devices.
A disadvantage of this known type of elevator is that relatively high tensions are necessary in the individual draw cables, and thus corresponding high forces are needed for their actuation, if the locking system is to respond exactly. This results in a correspondingly high cost for maintanence and inspection. Moreover, the "shortenings" and "lengthenings" of the draw cables which result from the pivoting of the pivot bodies are very slight, so that a very exact adjustment of cable tension is needed. Another disadvantage is that the "lengthening" or "shortening" introduced into the actuating draw cable corresponds substantially to that which is introduced into the (substantially longer) draw cables which run over the pivot bodies of the remaining telescopic sections. It is obvious that the cable elasticity inherent in the longer draw cables neutralises part of this "lengthening" or "shortening" of the actuating draw cable.
The object of the invention is to provide an elevator which has a locking system with an increased accuracy of response and increased reliability with a reduced expenditure of force. Another object is to prevent neutralisation of the cable lengthening and shortening by cable stretch.